Proceed At Your Own PERIL: Quantifying Future Extinction Risk For New Zealand Marine Molluscs Through Paleontological Metrics

The fossil record provides a clear chronicle of life on Earth. It is the key to understanding the long-term patterns and processes that shape extinction, origination, and environmental and climatological change. Present-day patterns and processes risk being potentially misinterpreted when this information is overlooked; this becomes more relevant than ever when interpreting the current biodiversity crisis. This thesis explores the applicability of paleontological metrics to assess extinction risks for New Zealand marine molluscs across past, present, and future climate scenarios. The primary focus of this research is to quantify future extinction risks for marine molluscs in New Zealand and evaluate whether metrics such as the Paleontological Extinction Risk In Lineages (PERIL) metric can effectively accomplish this. The PERIL metric has been trialled and tested on bivalves within the fossil record and has produced paleontologically derived extinction risks for past, present, and future bivalve populations with relative consistency. The metric's robustness is highlighted by its ability to differentiate extinction risks based on class and functional traits, such as size, life habit, feeding habit, and motility; gastropods had more volatile extinction rates while small-bodied, epifaunal, carnivorous/parasitic and motile molluscs showed higher extinction rates. Furthermore, molluscs overall were more at risk during warming periods.

Integrating New Zealand’s comprehensive fossil data with PERIL's predictive capabilities reveals a concerning trend when projecting present and future extinction risks of marine molluscs. All extant families are projected to face increases in extinction risk by the late 22nd to early 23rd centuries. The findings indicate a clear escalation of extinction risks under higher emission scenarios; however, significant differences in extinction risk across RCP scenarios may not become apparent until 2300 for over half of the families, with a particularly sharp increase in risk under RCP 8.5; families such as Muricidae and Mytilidae demonstrate this, with marked increases in extinction risk under higher emission scenarios, and only evident by 2300. The connection between extinction risk and the geographic area identified by the PERIL metric becomes notably stronger at higher temperatures, highlighting the increasing importance of preserving broad geographic distributions of species as temperatures rise. Consequently, if New Zealand’s mollusc species face elevated extinction risks as PERIL predicts, the effects may not be noticeable until it is too late under high emission scenarios. In contrast, lower emission scenarios may allow for more manageable extinction risks through effective conservation efforts. These findings underscore the importance of long-term assessment metrics for extinction risk, as short-term projections commonly used in current assessments may not capture the full extent of these risks.

This study leverages New Zealand's rich marine fossil record to illustrate the significance and relevance of paleontological metrics for enhancing our understanding of biodiversity and extinction dynamics. It demonstrates the ability of Conservation Paleobiology to bridge the gap between historical and modern ecological research. The PERIL metric provides a framework for recognising future risks and, despite certain limitations of working with the fossil record, offers critical insights into the inherent impacts of anthropogenic climate change on marine ecosystems. The integration of paleontological insights with modern ecological data holds great potential for the development of more comprehensive conservation strategies. A multi-disciplinary approach to conservation, involving collaboration with mātauranga Māori systems, is needed to enrich conservation strategies and better address the challenges posed by anthropogenic climate change.